The purpose of the present application is to improve the measurement accuracy of a concentration measurement device of a treatment solution preparation device, without increasing the burden on a health care worker in a preliminary stage of a sustained gradual removal-type treatment or the like, and without adding unnecessary functions to a sensor. In one aspect of the present invention, a treatment solution preparation device (60) includes the following: a mixing circuit (70) in which a plurality of stock liquids are mixed； a concentration measurement device (71) for measuring the concentration of a mixed solution on the basis of electrical conductivity and temperature as respectively measured by an electrical conductivity sensor (120) and a temperature sensor (121)； an electrolytic solution supply means (72) which causes an electrolytic solution of a known concentration to flow into the mixing circuit (70)； and a calibration means (73) in which, upon the electrolytic solution of a known concentration being caused to flow into the mixing circuit (70) by the electrolytic solution supply means (72) and the electrical conductivity of the electrolytic solution being measured by the electrical conductivity sensor (120), on the basis of the difference between the measured electrical conductivity and the known electrical conductivity of the electrolytic solution, the calibration means calibrates the temperature sensor (121) from the correlation between the temperature and the electrical conductivity.L'objectif de la présente invention est d'améliorer la précision de mesure d'un dispositif de mesure de la concentration d'un dispositif de préparation d'une solution de traitement, et ce, sans alourdir la charge de travail d'un professionnel de santé lors d'une étape préliminaire d'un traitement de type épuration progressive prolongée ou équivalent, ni ajouter de fonctions inutiles à un capteur. La présente invention concerne, selon un aspect, un dispositif de préparation d'un
